Last updated: October 2026
Official source notice: Unlike the centralised ICRB Scientist/Engineer 'SC' exam, ISRO Technical Assistant (TA) recruitment is conducted centre-wise (VSSC, LPSC, SDSC-SHAR, URSC, SAC, IPRC, NRSC, HSFC, ISTRAC and others). Always check the advertisement released by the respective ISRO centre on isro.gov.in for centre-specific rules before applying.
For three-year Engineering Diploma holders, and B.E./B.Tech graduates who completed a Diploma first, the ISRO Technical Assistant is one of the most prestigious Group 'B' technical jobs in India. It starts directly at Pay Level 7 (₹44,900 – ₹1,42,400), with an approximate starting gross salary of ₹68,000 to ₹72,000+ per month depending on city class and DA. A Technical Assistant works hands-on in rocket integration, propulsion testing, satellite sub-systems, CAD/manufacturing and telemetry operations.
The exam tests core technical concepts with fast-paced numerical and conceptual questions, so it needs a different strategy from SSC JE or GATE. This guide covers the exam pattern, eligibility, branch-wise syllabus, books, Skill Test preparation and a 90-day plan.
| Quick facts | |
|---|---|
| Post / pay | Technical Assistant, Pay Level 7 (₹44,900 – ₹1,42,400) |
| Qualification | 3-year First-Class Diploma in Engineering (minimum 60%) |
| Age | 18 to 35 years, with relaxations as per Government of India rules |
| Written test | 80 MCQs, 90 minutes, +1 / -0.33 |
| Stage 2 | Skill Test, qualifying only (60/100 UR, 50/100 reserved) |
In this guide
Who is eligible for ISRO Technical Assistant?
Unlike Scientist/Engineer 'SC' (which needs a B.E./B.Tech degree), the Technical Assistant post is designed for First-Class Diploma Engineers.
Eligibility criteria (as per official ISRO centre notifications)
- Educational qualification: First-Class Diploma in Engineering (minimum 60% aggregate or equivalent CGPA, as specified by the State Board/AICTE), 3 years full-time, in the relevant discipline (Mechanical, Electronics, Computer Science, Civil, Electrical, Chemical, Automobile and so on) from a recognised institution.
- Age limit: 18 to 35 years as on the closing date of the notification, with 5 years relaxation for SC/ST and 3 years for OBC, plus relaxations for PwBD and Ex-Servicemen as per Government of India rules.
Important rule for B.E./B.Tech candidates
- B.Tech without a Diploma: candidates who went from 12th (HSC) straight to B.E./B.Tech are not eligible. ISRO notifications state that a higher degree cannot be treated as a substitute for the mandatory 3-year First-Class Diploma.
- Diploma + lateral-entry B.E./B.Tech: candidates who completed a 3-year First-Class Diploma first and later a B.E./B.Tech are eligible to apply on the basis of their Diploma certificate.
Exam pattern and selection process
Across almost all major ISRO centres (VSSC, LPSC, SDSC-SHAR, URSC, IPRC, HSFC, ISTRAC) the selection has two stages:
- Stage 1: Computer-Based Written Test (CBT). This decides your final merit rank.
- Stage 2: Skill Test (practical trade/lab assessment). It is strictly qualifying (Go / No-Go).
Standard written exam pattern (CBT)
In recent 2024–2026 notifications across SDSC-SHAR, VSSC, LPSC, IPRC and HSFC, ISRO follows a standard 80-question, 90-minute pattern.
| Parameter | Details |
|---|---|
| Mode | Online Computer-Based Test, objective MCQ |
| Total questions | 80 (core technical discipline plus applied engineering maths/physics) |
| Duration | 90 minutes (about 67 seconds per question) |
| Marking | +1 for every correct answer (80 marks total) |
| Negative marking | -0.33 (1/3rd) for every wrong answer |
| Qualifying marks (written) | Unreserved: 32/80 (40%). Reserved (SC/ST/OBC/PwBD): 24/80 (30%) |
| Skill Test shortlisting | Usually 1:5 (minimum 10 candidates per vacancy category), based on written marks |
| Skill Test qualifying marks | Unreserved: 60/100. Reserved: 50/100. These marks are not added to final merit |
Centre variations: While the latest standard is 80 marks (1 mark per question, -0.33 negative), a few older VSSC/LPSC papers awarded 3 marks per question (240 marks, -1 negative) or had 60 questions in 90 minutes. Whether a question carries 1 or 3 marks, the negative marking ratio is always 1/3rd and the syllabus stays core technical.
Branch-wise syllabus and weightage
ISRO does not publish a page-by-page syllabus in its recruitment PDF. It specifies that questions cover the 3-year Diploma curriculum of your branch. Based on an analysis of the last 12 years of VSSC, LPSC, URSC, SDSC-SHAR and HSFC papers, this is what shows up.
A. Mechanical Engineering (TA – Mechanical)
Nearly 65–70% of the paper comes from five foundational subjects.
| Subject | Weightage | Key topics |
|---|---|---|
| Manufacturing, Production & Workshop Technology | 18–22% | Metal cutting (orthogonal cutting, Merchant's circle, Taylor's tool life equation), lathe, milling, drilling, grinding, welding (TIG, MIG, resistance, defects), casting defects and riser design, metrology (limits, fits, tolerances, gauges, sine bar, surface roughness), CNC G-codes/M-codes |
| Strength of Materials & Engineering Mechanics | 15–18% | Equilibrium of forces, friction, trusses, centroid and moment of inertia, stress-strain diagrams, elastic constants (E, G, K, ν relationships), SFD and BMD, bending and torsion, thin cylinders, principal stresses, Euler's column buckling |
| Thermal Engineering (thermodynamics, heat transfer, IC engines/RAC) | 18–20% | Zeroth, first and second laws, Carnot/Otto/Diesel/Brayton/Rankine cycles, steam tables and dryness fraction, modes of heat transfer (composite walls, critical radius of insulation, Re, Pr, Nu, Gr), COP of refrigeration and heat pump |
| Fluid Mechanics & Hydraulic Machines | 12–15% | Viscosity, surface tension, capillarity, manometers, hydrostatic forces, continuity, Bernoulli's equation (venturimeter, orificemeter, pitot tube), laminar pipe flow (Hagen-Poiseuille), head losses (Darcy-Weisbach), impulse/reaction turbines, centrifugal/reciprocating pumps |
| Material Science, Theory of Machines & Machine Design | 15–18% | Iron-carbon diagram, heat treatment, crystal structures (BCC, FCC, HCP), mechanisms and inversions, gear trains, flywheels, governors, bearings, keys, riveted/welded joints, engineering drawing (orthographic projections, GD&T symbols) |
| Applied Maths & Basic Physics | 5–8% | Matrices, determinants, basic calculus (derivatives, definite integrals, maxima/minima), mensuration, units and dimensions |
B. Electronics & Communication (TA – Electronics)
| Subject | Weightage | Key topics |
|---|---|---|
| Electronic Devices & Analog Circuits | 20–25% | PN junction and Zener diode (regulator numericals), rectifiers (efficiency, ripple factor), BJT and MOSFET biasing/configurations, op-amp 741 (inverting/non-inverting gain, adder, integrator, CMRR, slew rate), oscillators (Barkhausen criterion, RC phase shift, Wien bridge) |
| Digital Electronics & Microprocessors/Microcontrollers | 18–22% | Number systems, Boolean algebra, K-maps, universal gates, MUX/DEMUX/adder/encoder, flip-flops, counters, shift registers, ADC/DAC resolution, 8085 microprocessor and 8051 microcontroller (pin diagram, addressing modes, interrupts, timer/counter registers) |
| Communication Systems & Electromagnetics | 15–18% | AM, FM, PM (modulation index and power), superheterodyne receiver, PCM, Nyquist rate, ASK/FSK/PSK/QPSK, optical fibre (numerical aperture, acceptance angle), satellite and radar basics, antennas and waveguides |
| Network Theory & Electronic Measurements | 15–18% | KCL, KVL, mesh/nodal analysis, Thevenin, Norton, superposition, maximum power transfer, RLC resonance, two-port networks, CRO (Lissajous), bridges (Wheatstone, Maxwell, Schering), transducers (LVDT, strain gauge, thermocouple, RTD, piezoelectric) |
| Control Systems, Power Electronics & Basic Electrical | 10–12% | Transfer function, damping ratio, time response of 1st/2nd order systems, Routh-Hurwitz, SCR/Triac/Diac, DC/AC motors and transformers basics |
C. Computer Science & Engineering (TA – CSE)
| Subject | Weightage | Key topics |
|---|---|---|
| C Programming, Data Structures & Algorithms | 22–25% | Pointers, arrays, structures, recursion output questions, stacks, queues, linked lists, trees (BST, AVL, traversals), graphs (BFS, DFS, Dijkstra, MST), searching/sorting and time complexities |
| Operating Systems & Computer Organization | 18–20% | Process scheduling (FCFS, SJF, Round Robin numericals), deadlocks (Banker's algorithm), semaphores, virtual memory and page replacement (FIFO, LRU, Optimal), cache mapping, pipelining, addressing modes |
| DBMS & SQL | 15–18% | ER diagrams, normalization (1NF to BCNF), SQL queries (GROUP BY, HAVING, JOIN, aggregates), transactions (ACID), indexing |
| Computer Networks & Web Technologies | 15–18% | OSI and TCP/IP layers, IPv4 subnetting, flow and error control (Stop-and-Wait, Go-Back-N, Selective Repeat, CRC), routing protocols, TCP/UDP ports, HTML/CSS/JavaScript and cybersecurity basics |
| Digital Logic & Software Engineering | 12–15% | Boolean minimization, flip-flops, number conversions, SDLC models (Waterfall, Agile, Spiral), testing (black-box, white-box, cyclomatic complexity) |
Best books and resources
Toppers and selected Technical Assistants of VSSC, LPSC and URSC describe a two-layer strategy: one concept handbook, two objective practice books, and the ISRO PYQs.
Mechanical Engineering
- Mechanical Engineering (Objective Type) by R.S. Khurmi & J.K. Gupta: around 35–45% of the single-line theory and formula questions in ISRO TA (especially SDSC-SHAR, IPRC and URSC) are at this level.
- Mechanical Engineering by R.K. Jain: for deeper production, metrology, workshop and thermal questions often asked by VSSC and LPSC.
- SSC JE previous year solved papers (Youth Competition Times / Made Easy) and GATE 1-mark PYQs: for fast numerical practice in SOM, thermodynamics and fluid mechanics.
Electronics & Communication
- A Handbook on Electronics Engineering (Made Easy) plus an objective book by Jairam Bhupesh / J.B. Gupta / R.K. Rajput: for quick formula revision and standard objective questions.
- Youth Competition Times (YCT) ISRO + RRB JE / SSC JE Electronics solved papers: covers previous VSSC, URSC, SAC and SDSC-SHAR TA Electronics papers in one place.
- ISRO Scientist 'SC' (ICRB) 1-mark questions and GATE ECE 1-mark PYQs: VSSC and URSC often lift old 1-mark questions directly.
Computer Science
- MCQ in Computer Science by Timothy J. Williams: ISRO papers have historically picked direct conceptual questions from it.
- GATE CSE 1-mark PYQs (GeeksforGeeks / Made Easy): best for C program outputs, OS scheduling numericals and IP subnetting.
Practise ISRO Technical Assistant (Mechanical) papers centre by centre, with solutions, on CMB HUB.
Why centre papers feel different
Not every ISRO centre sets the same style of paper.
- VSSC (Thiruvananthapuram) and LPSC (Valiamala/Bengaluru): the most conceptual and numerical-heavy papers. Expect 50–60% numerical and analytical questions, including basic calculus, mechanics derivations, fluid/thermal numericals and circuit analysis. Memorising one-liners alone will not clear VSSC/LPSC cutoffs.
- SDSC-SHAR (Sriharikota), IPRC (Mahendragiri), URSC (Bengaluru) and SAC (Ahmedabad): usually a balanced mix of about 60% direct conceptual/practical questions and 40% straightforward formula numericals, with noticeable emphasis on workshop technology, metrology, engineering drawing, instrumentation and manufacturing/lab practice.
90-day preparation plan
Phase 1: Days 1 to 40 – core fundamentals and formula mastery
- Build a formula and constants notebook. There is no calculator, virtual or physical, and you have only 67 seconds per question. Write down every formula, material property, dimensionless number and conversion factor.
- Daily target: cover one major subject every 6–7 days. Read the theory from your Diploma notes or a standard handbook and immediately solve 150–200 objective questions for that topic.
- Practise mental calculation: fractions, square roots, powers of 10, π ≈ 3.14 and trigonometric values, by hand.
Phase 2: Days 41 to 70 – centre-wise PYQ marathon
- Collect all available ISRO TA previous year papers (2012 to 2026) across VSSC, LPSC, SDSC-SHAR, URSC, SAC, IPRC, NRSC, HSFC and ISTRAC, which is easily 25 to 35 official papers.
- Solve one full PYQ paper every alternate day with a strict 90-minute timer.
- Analyse all four options. If a question asks about TIG welding, note three bullet points on MIG, SAW and electron beam welding next to it. Examiners routinely frame next year's question from the other three options.
- Supplement with easy/medium ISRO Scientist 'SC' (ICRB) 1-mark questions of your branch.
Phase 3: Days 71 to 90 – speed mocks, accuracy and negative-marking control
Take 10 to 12 full-length 80-question CBT mocks and use the two-round strategy inside the 90-minute window:
| Round | Time | What to do |
|---|---|---|
| Round 1 | First 50 minutes | Sweep all 80 questions. Solve every one-step theory question and direct formula numerical (under 45 seconds). Mark long numericals for review. You should bank 45–52 sure questions. |
| Round 2 | Next 35 minutes | Return to the marked numericals and solve them calmly. |
| Final check | Last 5 minutes | Audit your attempts. Avoid blind guessing: with -0.33 negative marking, six wrong guesses wipe out two correct marks. Aim for 65 to 72+ high-accuracy attempts. |
Stage 2: the Skill Test
Once you clear the written cutoff (usually 60 to 68+ out of 80 for UR, depending on paper difficulty and vacancies) you are called for the Skill Test in a 1:5 ratio.
- It is 100% qualifying (Go / No-Go). You need 60% (UR) or 50% (reserved). Final selection depends only on written test marks among those who pass the Skill Test.
| Branch | What the Skill Test usually includes |
|---|---|
| Mechanical / Automobile / Civil | Measuring components with vernier calipers, micrometers, height gauge, dial gauge or bevel protractor; identifying materials, cutting tools, gears or valves; creating a 2D/3D part in AutoCAD/SolidWorks or reading an engineering drawing; a basic workshop, lathe or fitting task. |
| Electronics / Electrical | Identifying passive/active components, reading colour codes, soldering or breadboard assembly (rectifier, op-amp amplifier, 555 timer, logic gate checks), and measuring voltage, frequency and phase with a multimeter, function generator and CRO/DSO. |
| Computer Science | Writing and running C/C++/Python programs, SQL queries on a database, Linux commands, basic networking or troubleshooting tasks. |
Frequently asked questions
Does the ISRO Technical Assistant exam have General Awareness, English or Reasoning?
In almost all major centres (VSSC, LPSC, SDSC-SHAR, URSC, IPRC, HSFC) the 80-question TA paper is 100% technical: your Diploma engineering subjects plus 4–6 questions on basic engineering maths and mensuration. Do not confuse ISRO Technical Assistant with ISRO Assistant/UDC, which is an administrative exam testing English, Quant, Reasoning and GK.
Is a calculator allowed in the ISRO TA CBT?
No. Neither physical calculators nor on-screen calculators are permitted. All numericals are designed to be solved by hand with approximations.
What is the promotion hierarchy for an ISRO Technical Assistant?
You join as Technical Assistant-A (Level 7), then move through periodic Merit Promotion Scheme (MPS) reviews to Technical Assistant-B (Level 8), Technical Assistant-C (Level 9), Technical Officer-A (Level 10, a gazetted officer post equivalent to Scientist/Engineer 'SC'), Technical Officer-B (Level 11) and higher.